Effect of altitude on the spatiotemporal signal characteristics of inversion face recognition

Abstract

High-altitude environments, can significantly impact cognitive functions, yet the neural mechanisms underlying altitude-induced changes in face recognition remain largely unexplored. This study aimed to examine the impact of high-altitude hypoxia on face recognition processes, with a specific focus on the modulation of the face inversion effect in event-related potentials across different altitude levels. A total of 120 participants were recruited and divided into four groups based on altitude: 347 m (low-altitude control), 2950 m, 3680 m, and 4530 m (high-altitude groups), with 30 participants in each group. Electroencephalography (EEG) was used to record brain activity, and event-related potentials components (P1 and N170) were analyzed to assess the effects of altitude on face processing, particularly regarding the face inversion effect. A significant altitude-dependent reduction in P1 amplitude was observed, with the 3680 m and 4530 m groups showing significantly lower amplitudes compared to the 347 m group (p < 0.05), and inverted faces elicited greater P1 amplitudes than upright faces (p = 0.035). N170 amplitude was significantly more negative for inverted faces compared to upright faces (p < 0.001), while the 4530 m group exhibited earlier N170 latencies than the other altitude groups (p < 0.05), suggesting possible neural adaptation to chronic hypoxia. The sLORETA results revealed progressive temporal lobe reorganization: the 4530 m group exhibited enhanced activation in superior temporal gyrus during inverted face processing, contrasting with diminished responses at moderate altitudes (3680 m). These findings provide neurophysiological evidence that high-altitude hypoxia significantly modulates face recognition processes, particularly the face inversion effect. The observed altitude-dependent alterations in ERP components suggest that hypoxia impacts both early sensory encoding (P1) and higher-order configural processing (N170).

Keywords: Event-related potentials; Face inversion effect; High-altitude hypoxia; Holistic processing; sLORETA.

Fig. 1

The experimental protocol used in our study. Note: Example of facial stimuli used in the experiment. Images were obtained from the CAS-PEAL Face Database.

Fig. 2

The ERP and topographic maps for inverted and upright faces across 347 m, 2950 m, 3680 m, and 4530 m regions. This figure illustrates the event-related potential (ERP) waveforms recorded from different regions in response to upright and inverted face stimuli. Each panel represents the averaged ERP waveforms for one of the four regions of interest.

Fig. 3

The image source of N170 of the plain group and the plateau group under the condition of inverted face. There was a significant activation for 4530 m than 347 m (p = 0.048) in the temporal lobe and superior temporal gyrus (BA 22 and 38). (A: 347 vs. 2950; B: 347 vs. 3680; C: 347 vs. 4530.). The data presented in this figure represent the average results from all participants.

Fig. 4

The image source of N170 of between the plateau group under the condition of inverted face. There was a significant activated for 4530 m than 3680 m (p = 0.008) in the temporal lobe, superior temporal gyrus, and sub-gyral (BA 22, 38, and 13). (A: 2950 vs. 3680; B: 4530 vs. 3680; C: 3680 vs. 4530). The data presented in this figure represent the average results from all participants.